Sulfide solid electrolyte and solid battery

Abstract

The present application relates to a sulfide solid electrolyte and a solid battery. The main object is to provide a sulfide solid electrolyte having good water resistance while maintaining a argyrodite-type crystal structure. In the present disclosure, the above problem is solved by providing a sulfide solid electrolyte having an argyrodite-type crystal phase, containing Li, Ge, Sb, S, I, and A, wherein A is an anion having a larger ionic radius than a sulfide ion.

Description

Technical Field

[0001] This disclosure relates to sulfide solid electrolytes and solid batteries. Background Technology

[0002] Solid-state batteries are batteries with a solid electrolyte layer between the positive and negative electrode layers. Compared to liquid batteries with electrolytes containing flammable organic solvents, they offer the advantage of simplified safety devices. Sulfide solid electrolytes are known as solid electrolytes for solid-state batteries.

[0003] Patent document 1 discloses a sulfide solid electrolyte containing lithium, phosphorus, sulfur and two or more elements X selected from halogen elements, containing a sulfosilver-germanium ore-type crystal structure, wherein the molar ratio of sulfur to phosphorus b (S / P) and the molar ratio of element X to phosphorus c (X / P) satisfy a specified relationship.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018-047565 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Sulfide solid electrolytes with a sulfide-germanium sulfide crystal structure, for example, have a composition represented by Li6PS5I. Furthermore, to improve oxidation resistance, sulfide solid electrolytes that replace P with Ge and Sb are being investigated. On the other hand, in sulfide solid electrolytes with a sulfide-germanium sulfide crystal structure, increasing the proportion of I (iodine) readily improves the water resistance of the sulfide solid electrolyte, but sometimes it is impossible to maintain the sulfide-germanium sulfide crystal structure.

[0009] This disclosure was made in view of the above-mentioned circumstances, and its main purpose is to provide a sulfide solid electrolyte that has good water resistance while maintaining the sulfide-germanium ore-type crystal structure.

[0010] Methods for solving problems

[0011] To address the aforementioned issues, this disclosure provides a sulfide solid electrolyte having a sulfide-germanium ore-type crystal phase containing Li, Ge, Sb, S, I, and A, wherein A is an anion having an ionic radius larger than that of a sulfide ion.

[0012] According to this disclosure, due to the presence of the A anion, it becomes a sulfide solid electrolyte that maintains the argyrocerium sulfide crystal structure and has good water resistance. Furthermore, according to this disclosure, the sulfide solid electrolyte contains Ge and Sb as cations, which have better oxidation resistance than P, thus becoming a sulfide solid electrolyte with good oxidation resistance.

[0013] In the above disclosure, the sulfide solid electrolyte may be free of P.

[0014] In the above disclosure, the sulfide solid electrolyte may contain P, and the proportion of P relative to the total of Ge, Sb and P may be less than 50 mol%.

[0015] In the above disclosure, A may include a polyatomic anion having multiple O atoms.

[0016] In the above disclosure, the polyatomic anion may contain C, S or N as a cation.

[0017] In the above disclosure, A may contain carbonate ions (CO3-). 2- ) and sulfate ions (SO4) 2- At least one of them.

[0018] In the above disclosure, A may contain bromide ions.

[0019] In the above disclosure, the sulfide solid electrolyte may have a composition of (2-ab)Li₂S-aLiI-bLi α The composition represented by A-Li4(Ge,Sb)S4 is such that a satisfies 0 < a < 2, b satisfies 0 < b < 2, a and b satisfy 0 < a + b < 2, and α is the value corresponding to the valence of A.

[0020] In the above disclosure, a and b can satisfy 1.5≤a+b≤1.9.

[0021] In the above disclosure, the above 'a' can satisfy 0.8≤a≤1.2.

[0022] In the above disclosure, b can satisfy 0.4≤b≤1.0.

[0023] In addition, this disclosure provides a solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the aforementioned sulfide solid electrolyte.

[0024] According to this disclosure, by using the above-described sulfide solid electrolyte, a solid battery with good water resistance is obtained.

[0025] The effects of the invention

[0026] The sulfide solid electrolyte disclosed herein exhibits the following effects: while maintaining the sulfide-germanium ore-type crystal structure, it also has good water resistance. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a method for manufacturing a sulfide solid electrolyte according to the present disclosure.

[0028] Figure 2 This is a schematic cross-sectional view illustrating a solid-state battery in this disclosure.

[0029] Figure 3 The results are from the XRD determination of the sulfide solid electrolyte obtained in Example 1.

[0030] Figure 4 The results are from the XRD determination of the sulfide solid electrolyte obtained in Comparative Example 1.

[0031] Figure 5 The results are from the XRD determination of the sulfide solid electrolyte obtained in Comparative Example 2.

[0032] Explanation of reference numerals in the attached figures

[0033] 1… Positive electrode layer

[0034] 2… Negative electrode layer

[0035] 3… Solid electrolyte layer

[0036] 4…Positive current collector

[0037] 5… Negative current collector

[0038] 6…battery casing

[0039] 10… Solid-state batteries Detailed Implementation

[0040] The following provides a detailed description of the sulfide solid electrolyte and solid battery disclosed herein.

[0041] A. Sulfide solid electrolytes

[0042] The sulfide solid electrolyte of this disclosure has a sulfide-germanium ore-type crystal phase and contains Li, Ge, Sb, S, I and A (A is an anion with an ionic radius larger than that of a sulfide ion).

[0043] According to this disclosure, due to the presence of the sulfide anion, it becomes a sulfide solid electrolyte that maintains a sulfide-germanium ore-type crystal structure while exhibiting good water resistance. Here, a typical composition of the sulfide solid electrolyte with a sulfide-germanium ore-type crystal structure is 2Li₂S-Li₃PS₄ (=Li₇PS₆). In this composition, the sulfide ions (S₂S) contained in Li₂S… 2- Unlike the sulfide ions (thioide ions that form PS bonds) contained in Li3PS4, LiI readily reacts with water. Therefore, we attempted to replace a portion of Li2S with LiI.

[0044] For example, a sulfide solid electrolyte with a composition represented by Li6PS5I is equivalent to (2-a)Li2S-aLiI-Li3PS4 where a = 1. On the other hand, to improve oxidation resistance, sulfide solid electrolytes with P replaced by Ge and Sb are being investigated. Such sulfide solid electrolytes are, for example, represented by (2-a)Li2S-aLiI-Li4(Ge,Sb)S4 (0 < a < 2). From the viewpoint of improving the water resistance of sulfide solid electrolytes, increasing the proportion of I (LiI) a is effective. However, when increasing the proportion of I, it is sometimes impossible to maintain the sulfide-germanium ore-type crystal structure. In this disclosure, by using an A anion with a larger ionic radius than sulfide ions in addition to I ions, it is possible to reduce the sulfur ions (S) contained in Li2S while maintaining the sulfide-germanium ore-type crystal structure. 2- The ratio of P to Sb is determined. As a result, a sulfide solid electrolyte with good water resistance is obtained. Furthermore, in this disclosure, the sulfide solid electrolyte contains Ge and Sb as cations, which have better oxidation resistance than P, thus becoming a sulfide solid electrolyte with good oxidation resistance.

[0045] The sulfide solid electrolyte of this disclosure has a sulfargillite-germanium-type crystalline phase. This sulfide solid electrolyte can be confirmed to have a sulfargillite-germanium-type crystalline phase by X-ray diffraction (XRD). Specifically, for the sulfide solid electrolyte, in XRD measurements using CuKα rays, peaks are preferably present at 2θ = 17.0° ± 0.5°, 24.1° ± 0.5°, 28.3° ± 0.5°, 29.6° ± 0.5°, and 38.6° ± 0.5°. These peaks are typical of the sulfargillite-germanium-type crystalline phase. The positions of these peaks can be within the range of ±0.3° or ±0.1°.

[0046] The sulfide solid electrolyte in this disclosure preferably contains a sulfide-germanium sulfide-type crystal phase as the main phase. "Main phase" refers to the crystal phase to which the strongest peak belongs in XRD measurements using CuKα rays. Furthermore, in XRD measurements of the sulfide solid electrolyte using CuKα rays, a Li I peak may or may not be observed.

[0047] The sulfide solid electrolyte of this disclosure contains Li, Ge, Sb, S, I, and A, wherein A is an anion having an ionic radius larger than that of a sulfide ion. The sulfide solid electrolyte contains at least Li, Ge, and Sb as cations. The sulfide solid electrolyte may contain only Li, Ge, and Sb as cations, or it may further contain other cations. Examples of other cations include P. In the sulfide solid electrolyte, the total proportion of Ge and Sb relative to all cations except Li is, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol% or more. Furthermore, the proportion of Ge relative to the total proportion of Ge and Sb is, for example, 1 mol% or more and 99 mol% or less, or 20 mol% or more and 80 mol% or less.

[0048] Sulfide solid electrolytes preferably do not contain phosphorus (P). This is because they exhibit good oxidation resistance. On the other hand, sulfide solid electrolytes may contain P. This is because they readily precipitate argyrocyanide-type crystal phases. The proportion of P relative to the total of Ge, Sb, and P is, for example, 50 mol% or less, and may be 30 mol% or less, or even 10 mol% or less. On the other hand, the aforementioned proportion of P is, for example, 1 mol% or more, and may be 5 mol% or more.

[0049] Sulfide solid electrolytes contain at least S, I, and A as anions. A is an anion with a larger ionic radius than the sulfide ion. Additionally, A is an iodide ion (I₂). - Anions other than A. Sulfide solid electrolytes may contain only one type of anion equivalent to A, or they may contain two or more types.

[0050] A is, for example, a polyatomic anion. A polyatomic anion preferably has multiple O atoms. A single oxygen ion (O...) 2- The ionic radius of is 140 pm, which is smaller than that of the sulfide ion (S). 2- The ionic radius of is 184 pm. On the other hand, polyatomic anions with multiple O atoms are generally larger than sulfide ions (S). 2- The ionic radius of ) is large.

[0051] Polyatomic anions can contain C, S, or N as cations. Examples of polyatomic anions containing C include the carbonate ion (CO3-). 2- ), bicarbonate ions (HCO3) - As polyatomic anions containing sulfur, examples include sulfate ions (SO42-). 2- ), sulfite ions (SO3) 2- Examples of polyatomic anions containing nitrogen include nitrate ions (NO3).- ), nitrite ions (NO2) - ).

[0052] A can be a monatomic anion. Typical examples of monatomic anions include halide ions (except iodide ions). Considering fluoride ions (136 pm), chloride ions (181 pm), and bromide ions (195 pm), bromide ions can be typically listed as monatomic anions equivalent to A.

[0053] Sulfide solid electrolytes may contain only S, I, and A as anions, or they may further contain other anions. Examples of other anions include Cl. In sulfide solid electrolytes, the total percentage of S, I, and A relative to all anions is, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. Furthermore, the molar ratio of A to I is, for example, 0.4 or more, or 0.6 or more. On the other hand, the molar ratio of A to I is, for example, 1.2 or less, 1.0 or less, or 0.8 or less.

[0054] Sulfide solid electrolytes preferably have (2-ab)Li₂S-aLiI-bLi α The composition shown is A-Li4(Ge,Sb)S4. In this composition, a satisfies 0 < a < 2, b satisfies 0 < b < 2, and a and b satisfy 0 < a + b < 2.

[0055] The value of 'a' is generally greater than 0, and can be 0.4 or greater, or 0.8 or greater. Conversely, the value of 'a' is generally less than 2, and can be 1.6 or less, or 1.2 or less. Similarly, the value of 'b' is generally greater than 0, and can be 0.2 or greater, or 0.4 or greater. The value of 'b' is generally less than 2, and can be 1.2 or less, or 1.0 or less. Furthermore, the values ​​of 'a' and 'b' are generally greater than 0, and can be 0.5 or greater, or 1.0 or greater, or 1.5 or greater. Conversely, the values ​​of 'a' and 'b' are generally less than 2, and can be 1.95 or less, or 1.9 or less.

[0056] Furthermore, in the above composition, α corresponds to the valence of A. For example, when A is carbonate ion (CO3-). 2- In the case of ), α is 2 (Li₂CO₃). For example, when A is bromide ion (Br₂CO₃), α is 2 (Li₂CO₃). - In the case of ), α is 1 (LiBr). Additionally, in the above composition, a portion of Ge or Sb can be replaced by P.

[0057] The sulfide solid electrolyte in this disclosure preferably exhibits high water resistance. The amount of H2S generated in the water resistance test described later is, for example, 25 ppm / h or less, but can be 20 ppm / h or less, or even 10 ppm / h or less. Furthermore, the sulfide solid electrolyte preferably has high ionic conductivity. The ionic conductivity at 25°C is, for example, 1 × 10⁻⁶. -4 S / cm or higher, or 5×10 -4 S / cm or higher.

[0058] Examples of shapes for sulfide solid electrolytes include particulate forms. Furthermore, the average particle size (D) of sulfide solid electrolytes... 50 For example, the particle size is greater than 0.1 μm and less than 50 μm. Average particle size (D) 50 The particle size distribution can be determined from the results of particle size distribution measurements based on laser diffraction scattering. There are no particular limitations on the applications of sulfide solid electrolytes; for example, they are preferred for use in solid-state batteries.

[0059] The method for manufacturing the sulfide solid electrolyte disclosed herein is not particularly limited. Figure 1 This is a flowchart illustrating a method for manufacturing the sulfide solid electrolyte of this disclosure. Figure 1 In this process, a raw material composition containing Li₂S, GeS₂, Sb₂S₃, Li₂I, and Li₂CO₃ is prepared. Next, the raw material composition is mixed, for example by mechanical grinding, to obtain a precursor (mixing step). Then, the obtained precursor is calcined to obtain a sulfide solid electrolyte (calcination step).

[0060] The above-described mixing process involves mixing a raw material composition containing Li, Ge, Sb, S, I, and A to obtain a precursor. Examples of Li-containing raw materials include Li sulfides. Examples of Li sulfides include Li₂S. Examples of Ge-containing raw materials include Ge sulfides. Examples of Ge sulfides include GeS₂. Examples of Sb-containing raw materials include Sb sulfides. Examples of Sb sulfides include Sb₂S₃. Examples of S-containing raw materials include elemental sulfur and the various sulfides described above. Examples of I-containing raw materials include Li iodides (LiI). Examples of A-containing raw materials include Li salts.

[0061] In the mixing process, a precursor (sulfide glass) is obtained by mixing the raw material composition. Examples of methods for mixing the raw material composition include mechanical grinding such as ball milling and vibratory milling. Mechanical grinding can be dry or wet; from the viewpoint of homogenization, the latter is preferred. There are no particular limitations on the type of dispersion medium used in wet mechanical grinding.

[0062] Various conditions for mechanical grinding are set in order to obtain the desired precursor. For example, when using a planetary ball mill, the raw material composition and grinding balls are added, and the mixture is processed at a specified rotational speed and time. The rotational speed of the planetary ball mill disc is, for example, 150 rpm or more. On the other hand, the rotational speed of the planetary ball mill disc is, for example, 500 rpm or less, or even 250 rpm or less. Furthermore, the processing time of the planetary ball mill is, for example, 5 minutes or more, or even 10 minutes or more. On the other hand, the processing time of the planetary ball mill is, for example, 30 hours or less, or even 25 hours or less.

[0063] The firing process involves firing the aforementioned precursor. This yields the aforementioned sulfide solid electrolyte. The firing temperature is preferably, for example, above the crystallization temperature. Furthermore, the firing time is, for example, 1 hour or more, or possibly 2 hours or more. Alternatively, the firing time is, for example, 10 hours or less, or possibly 8 hours or less. Examples of firing atmospheres include, for example, an inactive gas atmosphere and a vacuum.

[0064] B. Solid-state batteries

[0065] Figure 2 This is a schematic cross-sectional view illustrating the solid-state battery of this disclosure. Figure 2 The solid-state battery 10 shown includes: a positive electrode layer 1 containing a positive electrode active material, a negative electrode layer 2 containing a negative electrode active material, a solid electrolyte layer 3 formed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 for collecting current in the positive electrode layer 1, a negative electrode current collector 5 for collecting current in the negative electrode layer 2, and a battery casing 6 for housing these components. Furthermore, at least one of the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layer 3 contains a sulfide solid electrolyte as described in "A. Sulfide Solid Electrolyte" above.

[0066] According to this disclosure, by using the above-described sulfide solid electrolyte, a solid battery with good water resistance is obtained.

[0067] 1. Positive electrode layer

[0068] The positive electrode layer in this disclosure is a layer containing at least a positive electrode active material. In addition to the positive electrode active material, the positive electrode layer may also contain at least one of a solid electrolyte, a conductive material, and a binder.

[0069] Examples of positive electrode active materials include oxide active materials. Specifically, examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other layered active substances in rock salt, LiMn2O4, Li(Ni) 0.5 Mn1.5 Spinel-type active substances such as O4, and olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0070] The surface of the positive electrode active material can be coated with a coating. This is because it can suppress the reaction between the positive electrode active material and the sulfide solid electrolyte. Examples of coating materials include LiNbO3, Li3PO4, and LiPON, which are Li ion-conducting oxides. The average thickness of the coating is, for example, 1 nm or more and 50 nm or less, and can be 1 nm or more and 10 nm or less.

[0071] The positive electrode layer in this disclosure preferably contains the aforementioned sulfide solid electrolyte. Furthermore, carbon materials can be used as conductive materials, for example. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). Fluorine-based binders such as polyvinylidene fluoride (PVDF) can be used as binders. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0072] 2. Solid electrolyte layer

[0073] The solid electrolyte layer in this disclosure is a layer containing at least a solid electrolyte. In addition to the solid electrolyte, the solid electrolyte layer may also contain a binder. The same applies to the solid electrolyte and the binder as described above. The solid electrolyte layer in this disclosure preferably contains the aforementioned sulfide solid electrolyte. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0074] 3. Negative electrode layer

[0075] The negative electrode layer in this disclosure is a layer containing at least a negative electrode active material. In addition to the negative electrode active material, the negative electrode layer may also contain at least one of a solid electrolyte, a conductive material, and a binder.

[0076] Examples of anode active materials include metallic active materials and carbon active materials. Examples of metallic active materials include In, Al, Si, and Sn. On the other hand, examples of carbon active materials include mesophase carbon microspheres (MCMB), highly oriented thermally decomposable graphite (HOPG), hard carbon, and soft carbon.

[0077] Regarding the solid electrolyte, conductive material, and binder, the same applies as described above. The negative electrode layer in this disclosure preferably contains the aforementioned sulfide solid electrolyte. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0078] 4. Other structures

[0079] The solid-state battery disclosed herein typically includes a positive current collector for collecting current from the positive electrode active material and a negative current collector for collecting current from the negative electrode active material. Examples of materials for the positive current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of materials for the negative current collector include SUS, copper, nickel, and carbon. Furthermore, the battery casing can be a general battery casing, such as an SUS battery casing.

[0080] 5. Solid-state batteries

[0081] The solid-state battery disclosed herein is preferably a lithium-ion battery. Furthermore, the solid-state battery can be a primary battery or a secondary battery, with a secondary battery being preferred. This is because it can be repeatedly charged and discharged, for example, it can be used as a vehicle battery. Moreover, a secondary battery also includes the primary battery use of a secondary battery (used for a single discharge after charging). Additionally, examples of solid-state battery shapes include coin-shaped, stacked, cylindrical, and square types.

[0082] Furthermore, this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any technical solution having a structure that is substantially the same as the technical concept described in the patent claims of this disclosure and performing the same effect is included within the technical scope of this disclosure.

[0083] Example

[0084] [Example 1]

[0085] Li₂S (Fluoruchi Chemical, 0.8567 g), GeS₂ (High Purity Chemical, 0.4857 g), Sb₂S₃ (High Purity Chemical, 0.9048 g), S (High Purity Chemical, 0.1708 g), LiI (High Purity Chemical, 1.1883 g), and Li₂CO₃ (High Purity Chemical, 0.3936 g) were mixed in a mortar to obtain a raw material composition. This raw material composition, along with zirconia balls, was placed in a zirconia jar (500 ml) and mechanically ground at 300 rpm for 20 hours using a planetary ball mill (Fritch P-5). This yielded a precursor. The precursor was heated for 6 hours under an Ar atmosphere at a temperature above its crystallization temperature. This yielded a sulfide solid electrolyte. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLiI-bLi₂CO₃-Li₄(Ge 0.4 Sb 0.6 ) a=1.0, b=0.6 in S4.

[0086] [Example 2]

[0087] The composition of the raw material composition was changed to Li₂S (0.7201g), GeS₂ (0.4512g), Sb₂S₃ (0.8409g), S (0.1587g), LiI (1.1039g), and Li₂CO₃ (0.4875g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLiI-bLi₂CO₃-Li₄(Ge 0.4 Sb 0.6 ) a=1.0, b=0.8 in S4.

[0088] [Example 3]

[0089] The composition of the raw material composition was changed to Li₂S (0.7201g), GeS₂ (0.4512g), Sb₂S₃ (0.8406g), S (0.1587g), LiI (1.1039g), and Li₂SO₄ (0.7255g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLiI-bLi₂SO₄-Li₄(Ge 0.4 Sb 0.6 ) a=1.0, b=0.8 in S4.

[0090] [Example 4]

[0091] The composition of the raw material composition was changed to Li₂S (0.7846 g), GeS₂ (0.4961 g), Sb₂S₃ (0.8739 g), S (0.1650 g), LiI (1.1477 g), and LiBr (0.5957 g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLiI-bLiBr-Li₄(Ge 0.4 Sb 0.6 ) a=1.0, b=0.8 in S4.

[0092] [Comparative Example 1]

[0093] The composition of the raw material composition was changed to Li₂S (1.3083 g), GeS₂ (0.5769 g), P₂S₅ (0.7033 g), and LiI (1.4115 g), and a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-a)Li₂S-aLiI-Li₄(Ge 0.4 P 0.6 In S4, a = 1.0.

[0094] [Comparative Example 2]

[0095] The composition of the raw material composition was changed to Li₂S (1.144 g), GeS₂ (0.5045 g), Sb₂S₃ (0.9398 g), S (0.1774 g), and Li₂I (1.2342 g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-a)Li₂S-aLi₂I-Li₄(Ge 0.4 Sb 0.6 In S4, a = 1.0.

[0096] [Comparative Example 3]

[0097] The composition of the raw material composition was changed to Li₂S (0.7934 g), GeS₂ (0.4498 g), Sb₂S₃ (0.8379 g), S (0.1582 g), and Li₂I (1.7607 g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-a)Li₂S-aLi₂I-Li₄(Ge 0.4 Sb 0.6 In S4, a = 1.6.

[0098] [Comparative Example 4]

[0099] The composition of the raw material composition was changed to Li₂S (0.6928 g), GeS₂ (0.4341 g), Sb₂S₃ (0.8087 g), S (0.1527 g), and Li₂I (1.9117 g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-a)Li₂S-aLi₂I-Li₄(GeS₂S-aLi₂I-Li₄) 0.4 Sb 0.6 In S4, a = 1.8.

[0100] [Comparative Example 5]

[0101] The composition of the raw material composition was changed to Li₂S (0.8104 g), GeS₂ (0.5078 g), Sb₂S₃ (0.946 g), S (0.1786 g), Li₂I (1.2424 g), and LiCl (0.3148 g). Otherwise, the procedure was the same as in Example 1 to obtain a sulfide solid electrolyte. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLi₂I-bLiCl-Li₄(Ge 0.4 Sb 0.6 In S4, a = 1.0 and b = 0.8. It should be noted that chloride ions (Cl...) -The ionic radius of ) is greater than that of sulfide ions (S) 2- The ionic radius is small.

[0102] [Comparative Example 6]

[0103] The composition of the raw material composition was changed to Li₂S (0.8815 g), GeS₂ (0.5524 g), Sb₂S₃ (1.0290 g), S (0.1943 g), and Li₂CO₃ (1.3429 g). Otherwise, a sulfide solid electrolyte was obtained in the same manner as in Example 1. The composition of the obtained sulfide solid electrolyte is equivalent to (2-ab)Li₂S-aLi₂I-bLi₂CO₃-Li₄(Ge 0.4 Sb 0.6 ) a=0, b=1.8 in S4.

[0104] [evaluate]

[0105] (XRD measurement)

[0106] The sulfide solid electrolytes obtained in Examples 1-4 and Comparative Examples 1-6 were subjected to X-ray diffraction (XRD) measurements using CuKα rays. Representative results are shown in the figures for Example 1 and Comparative Examples 1 and 2. Figures 3-5 .like Figures 3-5 As shown, the sulfide solid electrolytes obtained in Example 1 and Comparative Examples 1 and 2 all exhibited a sulforaphane-germanium ore-type crystal phase. Furthermore, although not specifically illustrated, the sulfide solid electrolytes obtained in Examples 2-4 were also confirmed to have the same sulforaphane-germanium ore-type crystal phase as Example 1. On the other hand, in the sulfide solid electrolyte obtained in Comparative Example 3, in addition to the peak of the sulforaphane-germanium ore-type crystal phase, a Li I peak was also confirmed. Furthermore, the sulfide solid electrolytes obtained in Comparative Examples 4-6 did not exhibit the sulforaphane-germanium ore-type crystal phase.

[0107] (Water resistance test)

[0108] Water resistance tests were conducted on the sulfide solid electrolytes obtained in Examples 1-4 and Comparative Examples 1-6. Specifically, a 1.5L desiccator was placed in a dry air glove box at a dew point of -30°C, and an Al container containing 2g of sulfide solid electrolyte was placed inside the desiccator. The desiccator lid was closed, and the mixture was left to stand for 1 hour with the fan on. The amount of H2S generated during this time was observed using a sensor, and the amount generated per unit time was calculated. The results are shown in Table 1.

[0109] (Measurement of ionic conductivity)

[0110] The ionic conductivity of the sulfide solid electrolytes obtained in Examples 1-4 and Comparative Examples 1-6 was measured (25°C). Specifically, 100 mg of the obtained sulfide solid electrolyte powder was placed in a ceramic cylinder along with a current collector and subjected to a pressure of 6 tons / cm². 2 The cells were pressed to produce pressure powder cells. For each pressure powder cell, AC impedance was measured at room temperature, and the ionic conductivity was determined from the resistance value and the thickness of the pressed sheet. The results are shown in Table 1.

[0111] [Table 1]

[0112]

[0113] As shown in Table 1, it was confirmed that in Examples 1-4, although the conductivity was lower than that of Comparative Example 1, the amount of H2S was significantly lower. This is presumably because the sulfide solid electrolytes obtained in Examples 1-4 did not contain phosphorus (P). Furthermore, in Examples 1-4, the amount of H2S was lower than that of Comparative Example 2. This is presumably because the sulfide solid electrolytes obtained in Examples 1-4 contained anions with ionic radii larger than sulfide ions, thus reducing the amount of isolated sulfur (S).

[0114] Here, as shown in Comparative Examples 3 and 4, increasing the proportion of the first anion makes it difficult to obtain a sulfide solid electrolyte with a sulfide-germanium sulfide crystal phase. Furthermore, as shown in Comparative Example 5, even when using Cl ions (ions with a smaller ionic radius than sulfide ions) as the second anion, it is impossible to obtain a sulfide solid electrolyte with a sulfide-germanium sulfide crystal phase. Additionally, as shown in Comparative Example 6, even when not using I ions as the first anion and increasing the proportion of CO3 ions as the second anion, it is impossible to obtain a sulfide solid electrolyte with a sulfide-germanium sulfide crystal phase. However, in Examples 1-4, using I ions as the first anion and then using A anion as the second anion improves water resistance while maintaining the sulfide-germanium sulfide crystal phase.

Claims

1. A sulfide solid electrolyte having a sulfide-germanium ore-type crystal phase, containing Li, Ge, Sb, S, I, and A, among which... A is an anion with a larger ionic radius than the sulfide ion. The sulfide solid electrolyte has a composition of (2-ab)Li₂S-aLiI-bLi α The composition represented by A-Li4(Ge,Sb)S4, wherein a satisfies 0 < a < 2, b satisfies 0 < b < 2, a and b satisfy 0 < a + b < 2, and α is a value corresponding to the valence of A.

2. The sulfide solid electrolyte according to claim 1, wherein, The A contains a polyatomic anion having multiple O atoms.

3. The sulfide solid electrolyte according to claim 2, wherein, The polyatomic anion contains C, S, or N as cations.

4. The sulfide solid electrolyte according to claim 1, wherein, A contains carbonate ions (CO3). 2- and sulfate ions SO4 2- At least one of them.

5. The sulfide solid electrolyte according to claim 1, wherein, The A contains bromide ions (Br). - .

6. The sulfide solid electrolyte according to claim 1, wherein, The condition 'a' and 'b' satisfy 1.5 ≤ a + b ≤ 1.

9.

7. The sulfide solid electrolyte according to claim 1, wherein, The condition 'a' satisfies 0.8 ≤ a ≤ 1.

2.

8. The sulfide solid electrolyte according to claim 1, wherein, The condition b satisfies 0.4 ≤ b ≤ 1.

0.

9. A solid-state battery is a battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein, At least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a sulfide solid electrolyte as described in any one of claims 1-8.

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